In this paper we describe new diode-chain triggering silicon controlled rectifiers (SCR) circuits for electro static discharge (ESD) protection purpose. Within this scheme, the trigger and holding voltages of SCRs can be changed according to the diode number and location in the SCR circuit. Breakdown mechanism is not the requirement for the operation of the SCRs. The SPICE simulation and experimental data are used to verify the performance of SCR circuits and to illustrate the circuit design principle, and good ESD I-V characteristics of the protection circuits are demonstrated.